Validate all json field present in the schema

[eugenemiretsky]

If a message is sent with additional keys that were not specific in the schema, the extra fields get omitted, and the message is written successfully.
The expected behavior would be for the request to fail until the schema is evolved.

Example request
{  
   "value_schema":"{ \"name\": \"Test\", \"type\": \"record\", \"namespace\": \"com.acme.avro\", \"fields\": [ { \"name\": \"customer_id\", \"type\": \"string\" } ] }",
   "records":[  
      {  
         "value":{  
            "extraFieldNotInSchema":"1234",
            "customer_id":"1107236512"
         }
      }
   ]
}